In the prior art, cathode ray tube oscilloscopes have been used for the display of patterns produced by deflecting an electron beam of the tube along a horizontal axis in proportion to a first signal and simultaneously deflecting the electron beam along a vertical axis in proportion to a second signal. When the first and second signals are harmonically related, the resultant patterns are stationary and information may be derived from the pattern shape. In particular, when the signals are harmonically related sinusoids, the resultant patterns are termed Lissajous patterns. When the signals are not harmonically related the patterns change in time, often going through pleasing permutations. Stereophonic signals have been displayed in this manner for both the purposes of obtaining information from the displayed patterns and for the aesthetic appearance of the patterns permutations.
Recently, color cathode ray tubes have been proposed as displays for the patterns produced by stereophonic signals wherein the patterns might be colored in sympathy with these signals to enhance the aesthetic appearance of the displayed patterns. In U.S. Pat. No. 3,627,912 to Hearn, issued Dec. 19, 1971, it was proposed that the color of a pattern produced by stereophonic signals be modulated in accordance with the instantaneous velocity of the electron beam. A relatively large number of circuit elements are required to achieve that technique of color modulation which requires the instantaneous variation of the proportions of current emitted from the three guns of a color picture tube.
To provide a commercially acceptable multicolor aesthetic cathode ray tube display apparatus for electrical signals, a small number of inexpensive parts must be used in order to minimize the cost of such a display.